The sight of arachnids often evoke fear or loathing in people. Indeed, there is a name for an abnormal fear of spiders, arachnophobia, and it is one of the more common phobias. Also, some arachnids are indeed poisonous to people. However, most arachnids are unlikely to bite humans, and by and large arachnids perform valuable roles in ecosystems. They also provide benefits to people, such as helping to control levels of insects. Their variety adds to human enjoyment of nature, and the daddy longlegs are considered so beneficial that a legend has rise up around them that stepping on them is not good (in areas of sufficient rainfall), for it will cause rain.
The classification of mites and some other types within the arachnids shows the importance of lineage in grouping organisms, for mites lack the characteristic segmented body of arachnids. They are classified within that group because it is assumed that it was a trait that was lost in the process of mites coming on the foundation of organisms with such segmented bodies.